The build-up of liquids (most often water) in gas-producing wells is problematic, as the gas must pass through the water to enter the well and flow to surface. This causes the gas production rate to decrease, which eventually results in the gas no longer being capable of carrying entrained water to the surface. Over time, water saturation increases in the area surrounding the wellbore and the water level rises in the wellbore casing and creates back pressure that further restricts gas flow rates. Eventually gas production may cease altogether.
Liquid accumulation requires special attention in wells that have been fracture-stimulated. Specifically, fracture stimulation is used on wells in reservoirs with low permeability to gas near the wellbore. A well is fracture-stimulated by pumping a large amount of sand, transported in a liquid- or gel-carrier, into the formation. The low-permeability rock is fractured and propped open with the fracture sand pack (proppant pack), which has much higher permeability than the surrounding reservoir. The high-permeability fracture extends a distance away from the wellbore, providing a long flow conduit with a high surface area for gas to enter the wellbore. Fracture water, pumped into the reservoir in the form of the sand carrier, is often not fully recovered after the stimulation procedure. This water can create liquid-loading problems for a long period of time and later in a well's life, this water may enter the wellbore where often mistaken for liquids produced from the reservoir and deemed to be a permanent condition that may be associated with higher flow rates. When this occurs, a well is often presumed to be unsalvageable and is capped in preparation for abandonment.
The prior art teaches methods for removing water from the wellbore but does not teach methods for removing water from the reservoir or fracture proppant pack surrounding the wellbore.
Specifically, U.S. Pat. No. 2,061,865 teaches a system for removing water from a gas-producing well. The system relies on a compressor driving air through a Venturi located at the bottom of the tubing, which in turn creates a vacuum for drawing water out of the well casing.
U.S. Pat. No. 4,171,016 teaches a device wherein water is removed once gas pressure drops below a certain level. As the water level rises, a float rises with the water and exposes a number of apertures. Drive water is injected into a chamber, generating a vacuum that causes well water to be drawn into the apertures.
U.S. Pat. No. 5,335,728 teaches a method of vaporizing water drawn off from a gas well into steam.